Level Design Issues

I am trying to create a level in unity using a modular asset pack i got from the unity store, but when i try to use snapping and vertex snapping, there is still holes on the side of the walls or seams where light comes through. This is supposed to be a horror game that is in the dark, so i have white lines all over my level. The game i am making is small, and is in one scene and is a 3 story house, should i create the level in blender first and import it into unity? Use pro builder? Or is there something i am not doing correctly?

It sounds like something to ask the asset creator, but as someone who constantly seems to butt heads with the lighting system…

Are these “modular” parts merely touching by an edge? That is often insufficient to block light seeping through. The parts should be touching solid face to face, or overlap for at least a small amount like 0.1 units in length.

Typically light bleeding mostly happens when geometry isn’t “solid” enough. You can also add light blockers (shadow caster objects).

Light will bleed through non-connected edges and so yes, you’ll need to make seamless models of your buildings. If you don’t want to do this then you could try setting the outdoor ambient lighting to black.

You can adjust snapping in Scene View to be lower value by 0.01-0.02, thats will insure overlapping. Doing everything in blender is time consuming, with pro-builder maybe, but unnecessary.

If issue persists with lower snapping value, you could place solid cubes along the walls with Shadows Only and set your walls Cast Shadows to Off to avoid rendering shadows twice.